<a href="http://www.flickr.com/photos/45699481@N04/4873389904/sizes/m/in/photostream/">Schmeegan on Flickr</a> Banks have the most to lose if the PIIGS (Greece, Italy, etc.) go belly up.

Despite reassurances from EU leaders that they would step in to ensure the viability of banks and even Greek bonds -- and the surging Euro markets -- it is quite possible that all that will go down the drain if the now inevitable "selective default" goes awry.

So who's in the most trouble.

We took a list of the largest European banks by assets and compared their market cap, common equity, and total exposure to PIIGS debt (thank you for the bank statistics, EBA!). Then we calculated exposure to PIIGS debt (sovereign and private) as a percentage of the banks' common equity. (Notice that HSBC, ING, and even Societe Generale are all absent from this list.)

The worst 20 cutoff for our test ended up being exposure equal to about 175% of common equity, but it really gets out of control once you get to the PIIGS banks (#1-9).

Remember our Italian and Irish friends who passed last week's stress tests? They're at the top of our list of big banks to be in trouble if things go bad.